[Mesa-dev] [PATCH 3/9] i915: Use L8A8 instead of I8 to simulate A8 on gen2

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Gen2 doesn't support the A8 texture format. Currently the driver
substitutes it with I8, but that results in incorrect RGB values.
Use A8L8 instead. We end up wasting a bit of memory, but at least
we should get the correct results.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=72819
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80050
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38873
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 src/mesa/drivers/dri/i915/i830_texstate.c   |  2 --
 src/mesa/drivers/dri/i915/i915_context.c    |  3 ++-
 src/mesa/drivers/dri/i915/intel_tex_image.c | 22 ++++++++++++++++++++++
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i915/i830_texstate.c b/src/mesa/drivers/dri/i915/i830_texstate.c
index 58d3356..b1414c7 100644
--- a/src/mesa/drivers/dri/i915/i830_texstate.c
+++ b/src/mesa/drivers/dri/i915/i830_texstate.c
@@ -47,8 +47,6 @@ translate_texture_format(GLuint mesa_format)
       return MAPSURF_8BIT | MT_8BIT_L8;
    case MESA_FORMAT_I_UNORM8:
       return MAPSURF_8BIT | MT_8BIT_I8;
-   case MESA_FORMAT_A_UNORM8:
-      return MAPSURF_8BIT | MT_8BIT_I8; /* Kludge! */
    case MESA_FORMAT_L8A8_UNORM:
       return MAPSURF_16BIT | MT_16BIT_AY88;
    case MESA_FORMAT_B5G6R5_UNORM:
diff --git a/src/mesa/drivers/dri/i915/i915_context.c b/src/mesa/drivers/dri/i915/i915_context.c
index 7f43896..3fd571d 100644
--- a/src/mesa/drivers/dri/i915/i915_context.c
+++ b/src/mesa/drivers/dri/i915/i915_context.c
@@ -109,7 +109,8 @@ intel_init_texture_formats(struct gl_context *ctx)
    ctx->TextureFormatSupported[MESA_FORMAT_B5G5R5A1_UNORM] = true;
    ctx->TextureFormatSupported[MESA_FORMAT_B5G6R5_UNORM] = true;
    ctx->TextureFormatSupported[MESA_FORMAT_L_UNORM8] = true;
-   ctx->TextureFormatSupported[MESA_FORMAT_A_UNORM8] = true;
+   if (intel->gen == 3)
+      ctx->TextureFormatSupported[MESA_FORMAT_A_UNORM8] = true;
    ctx->TextureFormatSupported[MESA_FORMAT_I_UNORM8] = true;
    ctx->TextureFormatSupported[MESA_FORMAT_L8A8_UNORM] = true;
 
diff --git a/src/mesa/drivers/dri/i915/intel_tex_image.c b/src/mesa/drivers/dri/i915/intel_tex_image.c
index 57674b9..be9a4ff 100644
--- a/src/mesa/drivers/dri/i915/intel_tex_image.c
+++ b/src/mesa/drivers/dri/i915/intel_tex_image.c
@@ -14,6 +14,7 @@
 #include "main/texobj.h"
 #include "main/teximage.h"
 #include "main/texstore.h"
+#include "main/texformat.h"
 
 #include "intel_context.h"
 #include "intel_mipmap_tree.h"
@@ -362,9 +363,30 @@ intel_image_target_texture_2d(struct gl_context *ctx, GLenum target,
                                   image->tile_x, image->tile_y);
 }
 
+static mesa_format intel_choose_tex_format(struct gl_context *ctx,
+                                           GLenum target,
+                                           GLint internalFormat,
+                                           GLenum format, GLenum type)
+{
+   struct intel_context *intel = intel_context(ctx);
+
+   switch (internalFormat) {
+   case GL_ALPHA:
+   case GL_ALPHA4:
+   case GL_ALPHA8:
+      /* no A8 on gen2 :( */
+      if (intel->gen == 2)
+         return MESA_FORMAT_L8A8_UNORM;
+      /* fall through */
+   default:
+      return _mesa_choose_tex_format(ctx, target, internalFormat, format, type);
+   }
+}
+
 void
 intelInitTextureImageFuncs(struct dd_function_table *functions)
 {
    functions->TexImage = intelTexImage;
+   functions->ChooseTextureFormat = intel_choose_tex_format;
    functions->EGLImageTargetTexture2D = intel_image_target_texture_2d;
 }
-- 
1.8.5.5